I agree a product like Felt might never feel as authentic as the real thing, but I don't think that's necessarily a problem.

Some people prefer to hand-write letters and will probably do so until they die. Some occasions require hand-written letters and will probably do so for a very long time to come. (Felt technically is hand-writing so I guess I mean non-digital hand-writing... Do we need to invent a new term?)

I don't think Felt is necessarily trying to compete with the above, it's simply trying to offer a middle-ground between text messages and inked letters. If we look at how quickly communication has changed (some might say devolved) over the last twenty years... wouldn't a product like Felt be a step in the right direction?